Wavelength dependence of the multiphoton ionization of CH3I by intense femtosecond laser pulses through Freeman resonances,Physical Chemistry Chemical Physics

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Wavelength dependence of the multiphoton ionization of CH3I by intense femtosecond laser pulses through Freeman resonances
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2022-11-22 , DOI: 10.1039/d2cp04308d
Ignacio M Casasús ₁ , María E Corrales ₁ , Luis Bañares _{1,

2}

Affiliation

Multiphoton ionization (MPI) of methyl iodide, CH₃I, has been investigated with the photoelectron imaging (PEI) technique, using high intensity femtosecond laser pulses at different central wavelengths. The use of high laser field strengths alters the way in which matter–radiation interaction takes place. This generates highly nonlinear phenomena, among which we can highlight the Stark shift effect. It can distort the potential energy surfaces of atoms and molecules, varying both the energy of electronic and rovibrational states of these systems and their ionization potentials. In this way, the Stark shift can generate resonances between intermediate states and an integer number of laser photons of a given wavelength, which would be absent in the low intensity regime. The main purpose of this work is the generation, detection and characterization of resonances produced by the Stark shift, commonly known as Freeman resonances, induced by multiphoton ionization of gas-phase CH₃I at different laser wavelengths. The results obtained reveal that a multitude of resonances are induced in the ionization of CH₃I in the range of intensities employed, involving several Rydberg states. Ionization pathways associated with different degrees of vibrational excitation in both the intermediate states and the molecular cation generated in each of the experiments are proposed.

中文翻译：

通过弗里曼共振的强飞秒激光脉冲对 CH3I 的多光子电离的波长依赖性

碘甲烷 CH _{3的多光子电离 (MPI)}I，已经用光电子成像 (PEI) 技术进行了研究，使用不同中心波长的高强度飞秒激光脉冲。高激光场强的使用改变了物质-辐射相互作用发生的方式。这会产生高度非线性现象，其中我们可以突出 Stark shift 效应。它可以扭曲原子和分子的势能面，改变这些系统的电子和振动状态的能量以及它们的电离势。通过这种方式，斯塔克位移可以在中间状态和给定波长的整数个激光光子之间产生共振，这在低强度状态下是不存在的。这项工作的主要目的是产生、检测和表征由斯塔克位移产生的共振，₃ I 在不同的激光波长下。获得的结果表明，在所采用的强度范围内，在 CH₃ I 的电离过程中会引发大量共振，涉及多个里德堡态。提出了与每个实验中产生的中间状态和分子阳离子中不同程度的振动激发相关的电离途径。

更新日期：2022-11-22

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